Heterogeneous populations of bone cells will be isolated by sequential digestion of mouse calvaria. Further separation of primary bone cell cultures that are enriched in osteoclast-like activities will be attempted. These cell populations are responsive to both PTH and calcitonin and the nature of the target cells for these hormones will be investigated. Changes in hyaluronic acid synthesis and cyclic AMP formation will be analyzed. Studies are planned to establish the types of protein kinases contained by bone tissue, and to note how these kinases segregate in populations of cells enriched for either osteoclast-like or osteoblast-like activities. The effects of PTH and calcitonin on these kinases, the involvement of calcium ions in these hormone induced changes, and the role the cell cycle plays in modulating hormone responsiveness will be examined. Finally, the growth conditions necessary for long term culture of differentiated bone cell types will be studied.